Brush assembly units



May 30, 1961 KENTARO TSUTSUMI 2,936,666

BRUSH ASSEMBLY UNITS Filed May 18, 1959 2 Sheets-Sheet 1 wa A ATTORNEYSMay 30, 1961 KENTARO TSUTSUMI BRUSH ASSEMBLY UNITS Filed May 18, 1959 IFab.

2 Sheets-Sheet 2 INVENTOR.

Kflv TARU 7 1/7 ATTORNEYS.

United States Patent BRUSH ASSEMBLY UNITS Kentaro Tsutsumi, Auburndale,Mass., assignor, by mesne assignments, to the United States of Americaas represented by the Secretary of the Navy Filed May 18, 1959, Set. No.814,120

9 Claims. (Cl. 310-247) This invention relates to brush assembly unitsby which an electrically conducting brush is mounted to yieldingly andresiliently press against a slip ring, commutator or other conductorsurface with which it is relatively movable.

Objects of the invention are to provide a brush mounting which can be ofa small size to match precision slip ring assemblies, which will havehigh current-carrying capacity, low friction, low contact resistance,long life, simple connections to electrical leads, ease of manufacture,assembly and installation, and which will be relatively simple, compact,practical, durable and inexpensive.

Other objects and advantages will be apparent from the followingdescription of an embodiment of the in vention and the novel featureswill be particularly pointed out hereinafter in connection with theappended claims.

In the accompanying drawing:

Fig. 1 is a longitudinal, sectional elevation of a unit constructed inaccordance with this invention, but with the brush holder unsectioned;

Fig. 2 is an end elevation of the same;

Fig. 3 is an end elevation of the same with the brush holder removed, asviewed along the line 33 of Fig. 1;

Fig. 4 is a side elevation of the complete unit;

Figs. 5 and 6 are side elevation and plan respectively of one step inthe manufacture of the volute spring and the attachment of its small endto the brush holder;

Fig. 7 is a side elevation of the volute spring at a later step in itsmanufacture; and

Fig. 8 is a plan of the complete volute spring as attached to the brushholder.

In the illustrated embodiment of the invention, the unit includes atubular or hollow housing or casing 1 of metal, having its main part ofa deep cup-shape that is closed at the open end of the cup by a metallicmember 2. The end of the casing which is closed by member 2 has anexternal peripheral flange 3 encircling the open end and within whichmember 2 is received and fixed, such as by welding or soldering. The endwall 4 of the casing that corresponds to the bottom of the cup, has aslot 5 extending diametrically across its exterior face for a depth atleast equal to the thickness of the end wall, which provides an aperturethrough that end wall from face to face.

A brush holder 6 extends endwise of itself through such aperture, andwithin the casing it has a head or flange 7 that slides in the casingand is guided thereby for endwise reciprocation of holder 6 in the slot5. The inner end 8 of the holder 6 beyound the flange 7 is a stem whichextends nearly to but terminates short of the opposite end of thecasing. The end closure 2 on its inner face has a projecting tongue 9with a deep recess 10 in its end face in which recess the inner free endof the stem 8 slides and is guided thereby. There is ample clearancebetween the free end of the stem 8 and the bottom of the recess 10 toenable substantial reciprocation of the stem 8 in recess 10 without thestem leaving that recess. The flange 7 limits reciprocation of theholder 6 in a direction out of the casing, and the inner end or bottomof recess 10 limits reciprocation of the holder 6 in the oppositedirection.

A brush 11 of any suitable material, such as of silvergraphite forexample, is secured in the outer free end of the holder 6, so as to forman endwise extension thereof for contact with a slip ring or commutationwhose relative position is shown by the dash line 12 in Fig. l.Silver-graphite brushes are disclosed, for example, in US. Patent#2,418,812.

Within the casing 1 and surrounding the stem 8 is a compression spring13 which is attached, such as by soldering, at one end to the stem 8near the flange 7, and at its other end to the casing 1 near the closure2. This spring 13 is under compression as installed, so as to alwaysurge the holder 6 in an outward direction until flange 7 abuts the endof the casing. This spring is preferably a volute spring surrounding thestem 8 and with its smaller diameter end soldered or otherwise fixed tothe stem 8 near the flange 7. The larger diameter end of the spring issoldered or otherwise fixed to the inner Wall of the casing as at 14,near the closure 2.

The closure 2 has a lug 15 extending from its outer face axially of thecasing, to which lug a suitable circuit conductor such as a springloaded socket wire terminal may be detachably connected. The closure 2is attached to the casing and soldered in closed position around itsperiphery after the brush holder and spring have been inserted into thecasing and the larger diameter end of the spring soldered to the casing.

The holder 6, where it passes through the slot 5 in the end wall of thecasing, may be formed of a cylindrical rod, but with parallel, oppositeflat faces 16 formed thereon to fit slidingly the opposite side Walls ofthe slot 5. This prevents rotation of the brush holder in the casingwithout limiting its sliding action in the slot. The slot is easilyformed by merely milling it across the end face of the casing for adepth at least equal to the thickness of that end wall of the casing.The sliding engagement of the cylindrical flange 7 with the interiorwall of the casing guides the holder in its reciprocations.

The volute spring 13 is formed of a flat metal ribbon 17 to give maximumcurrent carrying capacity. Its manufacture is illustrated in Figs. 5-8wherein a flat metal ribbon 17 of flexible resilient metal, such as shimstock brass, has one end soldered to the stem 8 near flange 7 as shownin Figs. 5 and 6. Then the ribbon 17 is wound spirally on the stem asshown in Fig. 7, and stretched endwise, as shown in Fig. 8.

The flange 3 of the casing has a flat area 18 (Fig. 2) which serves as aguide in aligning the brush holder unit with its mating ring, not shown,so that the unit may be easily and quickly mounted in or detached fromits holder assembly (not shown), with the brush 11 always properlypositioned with respect to a slip ring or commutator against which itabuts in use. This design permits easy and quick installation andremoval of each individual cartridge assembly. The brush is preferablyof silvergraphite because such material has a low constant contactresistance, high current carrying capacity, long life and low friction.The support of the brush holder 6 at both of its ends, provides accuracyof alignment of the brush.

The volute spring serves both as a spring loading member and a currentcarrying member, and with its fiat load deflection curve, when used inthis unit, tends to maintain a constant pressure of the brush tipagainst an eccentric or other mating slip ring, or against a commutator.The constant spring pressure is obtained with the use of a large crosssection of the spring, which in turn has a high current-carryingcapacity. This model of unit has carried a current of ten amperessatisfactorily and its maximum current-carrying capacity appears to bemuch greater, The spring pressure of the volute spring 13 can beadjusted by varying the free length of thespring.

It willbe understood. that various changes in the details, materials andarrangement of parts, which have been herein described and illustratedin order to explain the nature of the invention, may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the appended claims.

I claim:

1. A brush assembly unit comprising a hollow housing having an aperturein one end wall thereof, a brush holder extending through and sliding insaid aperture into said housing and there having a head which byengagement with said one end wall limits endwise movement of the holderin a direction out of the casing, and beyond said head a stern, a brushcarried by the outer end of said holder, the interior of said housinghaving means for guiding said stem during reciprocation of said holderin saidaperture, and a volute spring in said housing surrounding saidstem, with its small end fixed to said stem adjacent to said head, andits larger end fixed to the inner wall of said housing, and undercompression to hold said head against said apertured end wall.

2.. The unit according to claim 1, wherein the end of said housing,opposite from said end with the aperture, has an exterior endwiseextension formed to fit a spring loaded socket wire terminal.

3. The unit according to claim 1, wherein said aperture is a slot withopposite sides thereof fiat and parallel to oneanother, extendingentirely across and from face to face through that apertured end wall,and the part of said holder which slides in said aperture isnon-circular with opposite sides parallel to one another and conformingto and slidingly guided and held against rotation by the part of saidapertured end wall which defines the sides of said slot, whereby saidbrush holder and brush will be held against angular rotation whileslidable in said aperture.

4. The unit according to claim 1, wherein said stem guiding means is atongue on the inner face of the end wall of said housing opposite fromsaid apertured end, with a recess therein and extending in a directionlength- Wise of the housing and open at the free end of the tongue inwhich recess the inner end of the stem is slidingly received throughsaid open end, and guided for reciprocation as the brush holder moves indirections into and out of the housing.

5. The unit according to claim 1, wherein the end wall of said housingwhich is opposite from said apertured endwall has a stem exteriorv ofthe housing and extending;' approximately normal from thetouter face ofthat end wall for connection to a conductor.

6. A brush assembly unit comprising a cup-shaped, cylindrical, hollowcasing having an aperture in its end wall forming the cup bottom, abrush holder within the aperture, slidingly guided by the casing endwall defining the aperture, and extending in both directions from thatend wall, and with its inner end extending in a direction parallel tothe axis of the hollow casing, a brush secured to and forming anextension of the outer end of said holder, said holder having a lateralflange within the casing and engaging with the apertured end wall forlimiting removal of the holder from the casing, 21 voluteshaped springof ribbon-like metal disposed within the casing and surrounding theinner end of said holder, with the smaller diameter end of the springfixed to said holder near said lateral flange, and its larger diameterend fixed to the inner peripheral wall of said casing adjacent to thecasing end opposite from said apertured end, said spring beingcontinuously under compression. when within the casing, and a memberfixed to the open end of said casing and closing it, and having on itsinner face, and solely P within the casing, means slidingly guiding theinner end of said holder, and on its outer face means for connection toa conductor.

7. The brush assembly unit accordingv to claim 6, wherein said meansslidingly guiding the inner end of said holder is a partof said memberwith a recess aligned with the inner end of said holder in which thesaid inner end is received and slides endwise of itself as the guidance.

8. The unit according to claim 6, wherein said casing has an external,peripheral, non-circular flange adjacent the end which is closed by saidmember, for aligning the casing in a position in which said brush onsaid holder will be aligned with its mating ring.

9. A brush assembly unit comprising a hollow, generally cylindricalcasing having a slot with opposite, flat parallel side walls extendingtransversely across and through one end wall thereof, a brush holderextending through said slot into said casing and having opposite,parallel, flat side walls fitting and guided by said opposite slot sidewalls to prevent rotation of the holder while the holder is free toreciprocate endwise of itself in said slot, in directions into and outof the casing, the portion of said holder within said casing having aflange engageable with the inner face of said one end wall to limitmovement of said holder in a direction outwardly of the casing, theother end wall of said casing having a tongue projecting from its innerface toward said one end wall and having therein a recess extendinglongitudinally of the tongue and open at the free end of the tongue,said holder having a stem, inwardly of the casing beyond said flange,slidingly received in said recess in said tongue and guided thereby inits reciprocations, a volute spring in said casing surrounding saidstern and secured at its smaller end to said stern adjacent to saidflange, and at its other and larger end secured to said casing adjacentsaid other end wall, and a brush held in the outer, free end of saidholder, entirely exteriorly of said casing.

References'Cited in the file of this patent UNITED STATES PATENTS738,747 Acly Sept. 15', 1903 1,318,713 Aalborg Oct. 14, 1919 FOREIGNPATENTS 118,520 Great Britain Sept. 5, 1918 447,417 Germany July 26,1927

